When I put a metal roof on my house, the cellphone reception went from marginal to nearly nonexistent, so I bought a cellphone booster. My house is in a low area surrounded by trees. The system recommended by the manufacturer had an omnidirectional antenna. The installation instructions emphasized the importance of locating the outside antenna far from the inside antenna, so I put the antenna on the far end of the garage. The system ended up with 130 feet of co-ax from the outside antenna to the amplifier.
The inside reception was now a little bit better than the outside reception, but still marginal. The location was well within the reception area on the Verizon coverage map. When I called Verizon customer service they said that I was in a marginal reception area. So I went to the Verizon store. The salesman said that my make and model phone was not the best for reception in weak areas so I bought one of the phones he recommended. Reception was slightly better, but still marginal. I called the cellphone booster company and got nowhere.
Then winter came and reception improved slightly. At about that time, a co-worker got his amateur radio license, specializing in the 900 MHz band. That band is right next to one of the cellphone frequency bands, so I started picking his brain, after which another 900 MHz ham operator joined in. The signal loss in the 130 feet of co-ax was greater than the antenna gain. Based on their advice, I bought a directional antenna and mounted it closer to the amplifier. The new cable run was only 30 feet. They introduced me to the OpenSignal app, from which I found the direction to the nearest tower.
Cellphone reception was now excellent until spring. When the temperature rose above freezing, the reception became marginal again. I went back to the ham radio operators. The finger of suspicion pointed toward a red pine tree in front of the antenna. This tree had needles slightly over six inches long, exactly the right length to be half wave absorbers for 900 MHz radio waves. We figured that the sap was liquid and conductive in summer, frozen, and nonconductive in winter. So I cut the tree down and the problem was solved. I now have excellent cellphone reception in summer.
This was an interesting problem -- in that it had multiple causes -- all of which had to be solved in order to get to a final solution.
Jim Michler is a mechanical engineer. He has been getting paid to solve problems for more than 30 years, and has a number of patents as a result.
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